Molten metal may be one of the more difficult environments in which to maintain a pump due to the heat and corrosive factors within the molten metal. The submerged components of these pumps are typically made of graphite, ceramics or similar materials due to the ability of these types of material compositions to withstand the heat and corrosive effects of the molten metal environment. While references may be made herein to molten aluminum, this is only used to give an example and not to limit the invention to aluminum pumps, since the pump systems disclosed herein may be used for pumping other molten metals.
Despite the positive properties for this application, graphite and ceramics still corrode and deteriorate over time, and molten metal pumps must be more frequently maintained and replaced than other types of pumps. The replacement or servicing of a pump operating submersed in molten metal is a time consuming exercise. First the pump must be removed from the molten metal which generally causes downtime of the metal furnace if that is the application. Then the pump along with the molten metal contained thereon must be allowed to sufficiently cool to allow it to be disassembled.
Once the deteriorated components are sufficiently cool, the molten metal built up on the various pump surfaces must be sufficiently removed to allow disassembly and/or re-use of the pump components. Then the pump must be reassembled with the combination of old components or parts, along with the replacement parts. The downtime of a molten metal pump may be as much as two to three days before it is operational again, which illustrates the importance of increasing the useful life of the pumps.
In the disassembly of the pump, there are certain components which are typically cemented together in order to achieve a balanced and sufficiently rigid pump structure to allow continuous operation of the pump. However, when the pump must be disassembled, those cemented joints can be very difficult to disassemble.
For instance, in the case of a pump with vertical posts between the pump base and the motor mount structure, the posts have traditionally been cemented into bored holes within the base. When the pump is disassembled, the cemented portion of the posts must normally then be chipped, dug or drilled out in order to allow a new post to be placed in the same bore. This makes the disassembly much more difficult when certain replacement parts are being placed back into other parts which have already been in operation.
The combination of configuration and the number of components of typical pump systems makes them difficult to efficiently, accurately and quickly reassemble them. It is important that the motor, shaft, pump base and output conduit body be accurately aligned in order for the pump system to work efficiently once it is back in the molten metal. In some prior art pump systems, special jigs or other apparatus must be used to align the motor mount framework, the pump base, the pump shaft and the output conduit body. The combination of the components are very heavy, and because there are as many as four components which must be accurately aligned and then secured to one another, substantial time must be taken to assemble the pump system in the precise manner required by the application. Hence the need for a jig to assemble some prior art pumps.
It is an object of this invention to provide a pump which does not require as many or any cemented joints as the prior art pumps. It is also an objective of some of the embodiments of this invention to provide a pump and assembly system which tends to self-align the pump during the assembly process due to its design and configuration, reducing or eliminating the need for a jig or other alignment apparatus in some embodiments of the invention.